Method and apparatus for skid-off drilling

• US 5,407,302 A
• Filed: 02/11/1993
• Issued: 04/18/1995
• Est. Priority Date: 02/11/1993
• Status: Expired due to Fees

• Current Assignee: Santa Fe International Corp.
• Original Assignee: Santa Fe International Corp.
• Inventors: Hinton, Robert O., Springett, Charles N., Braddick, Peter W., Greenland, Roger A.
• Primary Examiner(s): CORBIN, DAVID
• Application Number:
  US08/016,604
• Time in Patent Office: 796 Days
• Field of Search: 405/195.1, 405/203, 405/209, 405/196, 405/201, 405/204, 405/224, 405/224.2
• US Class Current: 405/196
• CPC Class Codes: E02B 17/00 Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor construction methods for floating platforms B63B75/00; anchoring floating platforms B63B21/00; floating platforms, e.g. anchored, B63B35/44; underwater reservoirs B65D88/78
• CPC Class Codes: E02B 17/021 with relative movement between supporting construction and platform
• CPC Class Codes: E02B 2017/0047 using a barge
• CPC Class Codes: E02B 2017/0056 Platforms with supporting legs

Abstract

A different approach to tender assisted drilling which has the flexibility to be used with multiple jack-up rigs, and nearly any type of fixed offshore production platform. A skid base includes distinct capping beam feet and skid-off feet, the former adjustable to capping beam spacing and the latter restricted to support of the skid base upon cantilever beams. A special swivel mechanism and sliding mounting in the capping beam feet, and a vertical jack in the aft skid-off feet, enable the skid base to be transferred to the fixed platform simply by aligning them over the capping beams and depressurizing the skid-off feet. Thus, walking mechanisms may be swivelled and oriented upon the capping beams, notwithstanding relative movement between the jack-up rig and the platform. The skid base is simply walked across from the cantilever beams to the platform. The drill floor package is installed onto the skid base by raising and locking the cantilever beams into alignment with the skid base, while the skid base remains in a floating condition upon the fixed platform, and by skidding the drill floor package atop the skid base. The skid base may then be uncoupled from the cantilever and aligned with the platform using the walking and swivel mechanisms and the sliding mountings of the capping beam feet. Longitudinal and transverse movement abilities of the drill floor permit tender-assist drilling upon a variety of precise locations of the platform, and is readily supported from the jack-up rig with the aid of modular piping.

Claims

1. A method of transferring a skid base from a floatable jack-up rig having downwardly extendable legs engageable with the sea bed to raise the rig'"'"'s hull above the surface of the sea, the jack-up rig supporting the skid base on a pair of spaced parallel cantilever beams extending fore and aft in a longitudinal direction movably mounted on the jack-up rig, to a fixed platform spaced above the sea surface by a fixed plurality of platform legs engaging the sea bed, the fixed platform having a pair of spaced parallel capping beams also extending fore and aft in a longitudinal direction, using,

two longitudinally spaced, fore and aft pairs of skid-off feet mounted to the underside of the skid base with one skid-off foot of each pair resting on an associated one of the cantilever beams, the skid-off feet supporting the skid base for longitudinal movement along the cantilever beams, and

two longitudinally spaced pairs of fore and aft capping beam feet mounted to the underside of the skid base, the capping beam feet being engageable with the capping beams to support the skid base for longitudinal movement along the capping beams, the aft pair of capping beam feet being spaced aft of the aft skid-off feet and the fore pair of capping beam feet being spaced longitudinally between the fore and aft skid-off feet, each capping beam foot being mounted to the skid base for movement in a direction transversely of the skid base and for swivelling motion about a vertical axis relative to the skid base,

said method comprising the steps of:

maneuvering the jack-up rig in its floatable condition towards the fixed platform to a position in which the cantilever beams are generally aligned with and pointing towards the fore ends of the capping beams, in spaced relation thereto;

setting down the legs of the jack-up rig into contact with the sea bed and elevating the rig'"'"'s hull on the legs until the upper surfaces of cantilever beams are generally on a horizontal level with the upper surfaces of the capping beams, with the longitudinal axis of the cantilever beams limited to not more than a predetermined amount of misalignment relative to the longitudinal axis of the capping beams;

extending the cantilever beams on the jack-up rig aft until the aft ends of the cantilever beams are in closely spaced, adjacent relation to the fore ends of the capping beams;

moving the skid base aft on the cantilever beams, supported by the fore and aft pairs of skid-off feet, until the aft pair of capping beam feet are in overlapping adjacent relationship to the fore ends of the capping beams;

engaging the aft pair of capping beam feet with the capping beams for longitudinal sliding motion therealong end for simultaneous transverse sliding and swivelling movement relative to the skid base;

continuing the aft movement of the skid base, supported by the aft pair of capping beam feet and the fore pair of skid-off feet, until the fore pair of capping beam feet are in overlapping adjacent relationship to the capping beams;

engaging the fore pair of capping beam feet with the capping beams for longitudinal sliding motion therealong and for simultaneous transverse sliding and swivelling movement relative to the skid base; and

,

thereafter moving the skid base aft along the capping beams, supported on them by the fore and aft pairs of capping beam feet, until the skid base is entirely clear of the cantilever beams whereby the skid base is transferred from the cantilever beams of the jack-up rig to the capping beams of the fixed platform without imposing substantial transverse loads on the capping beams, despite any limited misalignment.

2. The method is described in claim 1, wherein a drill floor package is initially positioned upon the cantilever beams of the jack-up rig forward of the skid base for movement along the cantilever beams, the method including the following further steps after the skid base has been moved entirely clear of the cantilever beams:

withdrawing the cantilever beams in relation to the skid base a distance sufficient to entirely clear them from interference with the capping beams or the skid base;

raising the jack-up rig vertically until the upper surface of the cantilever beam lies in substantially the same horizontal plane as the upper surface of the skid base;

connecting the skid base and the cantilever beams to prevent relative movement between them while providing surfaces lying generally in the same horizontal plane as the upper surface of the skid base; and

,

moving the drill floor package longitudinally aft on the cantilever beams and onto the upper surface of the skid base.

3. A method of transferring drilling equipment, including a skid base, from a floatable jack-up rig having downwardly extendable legs engageable with the sea bed to raise the rig'"'"'s hull above the sea surface, the jack-up rig having, a pair of spaced parallel cantilever beams extending fore and aft upon a deck of the jack-up rig in a longitudinal direction and movably mounted on the rig, to a fixed platform supported above the sea surface by platform legs engaging the sea bed, the fixed platform having an elevated pair of spaced parallel capping beams also extending fore and aft in a longitudinal direction, wherein the skid base has mounted on its underside two longitudinally spaced, fore and aft pairs of skid-off feet, and two longitudinally spaced pairs of fore and aft capping beam feet, the skid off feet initially engaging the cantilever beams to support the skid base thereon, each of the aft pair of skit-off feet having a movement mechanism for selectively causing movement of the skid foot longitudinally along the associated cantilever beams in fore or aft directions, the capping beam feet being selectively engageable and dis-engageable from the capping beams and supporting the skid base on the capping beams when engaged therewith, each capping beam foot mounted on at least one skid base beam extending transversely across the underside of the base and having a movement mechanism for selectively causing movement of the capping foot longitudinally along an associated one of the capping beams when engaged therewith in fore or aft directions, a swivel mechanism that permits rotation of the capping foot relative to the skid base, and a sliding mounting that permits movement for the capping foot transversely of the skid base, the method comprising the steps of:

maneuvering the jack-up rig in the floatable condition to a position in which the aft ends of the cantilever beams are generally aligned with and pointing towards the fore ends of the capping beams in spaced relation thereto;

setting down the legs of the jack-up rig into the sea bed and elevating the rig'"'"'s hull until the upper surfaces of the cantilever beams are in generally the same horizontal plane as the upper surfaces of the capping beams, with not more than a predetermined limit of misalignment between their respective longitudinal axes;

moving the cantilever beams aft from the rig until their aft ends are in close proximity to the fore ends of the capping beams;

selectively operating the skid-off feet movement mechanisms to move the skid base aft along the cantilever beams until the pair of aft capping beam feet are positioned in overlapping relation to the pair of capping beams;

operating the swivel mechanisms and the sliding mountings of the aft pair of capping beam feet to align their movement mechanisms longitudinally with the associated capping beams to compensate for misalignment between the cantilever beams and the capping beams;

engaging the aft pair of capping beam feet with the capping beams for longitudinal motion therealong and for simultaneous swivelling and transverse movement of the skid base upon the aft capping beam feet;

disengaging the aft pair of skid-off feet from the cantilever beams;

continuing the aft movement of the skid base along the capping beams, supported by the aft capping beam feet and the fore skid-off feet, until the fore pair of capping beam feet are positioned in overlapping relation to the capping beams;

operating the swivel mechanisms and the sliding mountings of the fore pair of capping beam feet to align their movement mechanisms longitudinally with the associated capping beams to compensate for misalignment between the cantilever beams and the capping beams less than a predetermined limit;

engaging the fore pair of capping beam feet with the capping beams for longitudinal motion therealong and for simultaneous swivelling and transverse movement of the skid base on the fore capping feet; and

disengaging the fore pair of skid-off feet from the cantilever beams, whereby the skid base is transferred from the cantilever beams of the jack-up rig to the capping beams of the fixed platform without imposing substantial transverse loads on the capping beams despite any limited misalignment less than the predetermined limit.

4. The method as described in claim 3, wherein a drill floor package is initially positioned upon the cantilever beams of the jack-up rig forward of the skid base for movement along the cantilever beams, wherein the skid base includes a pair of spur beams projecting forwardly from the forward end of the skid base adjacent its upper surface, and wherein the cantilever beams include locking portions for engaging and disengaging the spur beams against relative longitudinal movement upon relative vertical motion into and out of engagement therewith, the method including the following further steps after the skid base has been transferred to the capping beams:

withdrawing the cantilever beams a short distance until they align vertically with the portions of the spur beams engageable by the locking portions of the cantilever beams;

raising the jack-up rig vertically on its legs until the locking portions of the cantilever beams engage with and lock to the spur beams to prevent relative longitudinal movement between said skid base and the cantilever beams, the upper surface of the skid base, the spur beams and the cantilever beams lying in substantially the same horizontal plane; and

moving the drill floor package longitudinally aft on the cantilever beams and across the spur beams onto the upper surface of the skid base.

5. A method according to claim 3, wherein:

the step of operating the swivel mechanisms and the sliding mountings of the aft pair of capping beam feet includes the step of

moving the aft capping beam feet along the sliding mountings until each aft capping foot is aligned transversely with its associated one of the capping beams; and

,

the step of operating the swivel mechanisms and the sliding mountings of the fore capping beam feet includes the step of

moving the fore capping beam feet along the sliding mountings until each fore capping foot is aligned transversely with its associated one of the capping beams.

6. A method according to claim 3, the skid base being generally rectangular in plan and having a longitudinal axis, wherein said method further comprises the step, after the skid base has been transferred to the capping beams, of aligning the longitudinal axis of the skid base with the capping beams using the swivelling mechanism and sliding mountings of the capping beam feet.

7. A method of transferring a skid base to a floatable jack-up rig having downwardly extendable legs engageable with the sea bed to raise the rig'"'"'s hull above the surface of the sea, the jack-up rig adapted to support the skid base on a pair of spaced parallel cantilever beams extending fore and aft in a longitudinal direction movably mounted on the jack-up rig, from a fixed platform spaced above the sea surface by a fixed plurality of platform legs engaging the sea bed, the fixed platform having a pair of spaced parallel capping beams also extending fore and aft in a longitudinal direction that support the skid base thereon, using,

two longitudinally spaced, fore and aft pairs of capping beam feet mounted to the underside of the skid base with one capping beam foot of each pair resting on an associated one of the capping beams, the capping beam feet supporting the skid base for longitudinal movement along the capping beams, each capping beam foot being mounted to the skid base for movement in a direction transversely of the skid base and for swivelling motion about a vertical axis relative to the skid base, and

two longitudinally spaced pairs of fore and aft skid-off feet mounted to the underside of the skid base, the skid-off feet being engageable with the cantilever beams to support the skid base for longitudinal movement along the cantilever beams, the aft pair of capping beam feet being spaced aft of the aft skid-off feet and the fore pair of capping beam feet being spaced longitudinally between the fore and aft skid-off feet,

said method comprising the steps of:

maneuvering the jack-up rig in its floatable condition towards the fixed platform to a position in which the cantilever beams are generally aligned with and pointing towards the fore ends of the capping beams, in spaced relation thereto;

setting down the legs of the jack-up rig into contact with the sea bed and elevating the rig'"'"'s hull on the legs until the upper surfaces of cantilever beams are generally on a horizontal level with the upper surfaces of the capping beams, with the longitudinal axis of the cantilever beams limited to not more than a predetermined amount of misalignment relative to the longitudinal axis of the capping beams;

extending the cantilever beams on the jack-up rig aft until the aft ends of the cantilever beams are in closely spaced, adjacent relation to the fore ends of the capping beams;

moving the skid base longitudinally forward on the capping beams, supported by the fore and aft pairs of capping beam feet, until the fore pair of skid-off feet are in overlapping adjacent relationship to the aft ends of the cantilever beams;

engaging the fore pair of skid-off feet with the cantilever beams for longitudinal sliding motion therealong and for simultaneous transverse sliding and swivelling movement of the aft pair of capping beam feet relative to the skid base;

continuing the forward movement of the skid base, supported by the aft pair of capping beam feet and the fore pair of skid-off feet, until the aft pair of skid-off feet are in overlapping adjacent relationship to the cantilever beams;

engaging the aft pair of skid-off feet with the cantilever beams for longitudinal sliding motion therealong; and

,

disengaging the aft pair of capping beam feet from the capping beams, whereby the skid base is transferred to the cantilever beams of the jack-up rig from the capping beams of the fixed platform without imposing substantial transverse loads on the capping beams, despite any limited misalignment.

8. A method according to claim 7, wherein the step of moving the skid base longitudinally forward on the capping beams, supported by the fore and aft pairs of capping beam feet, until the fore pair of skid-off feet are in overlapping adjacent relationship to the aft ends of the cantilever beams, further includes the step of advancing the capping beam feet non-synchronously and thereby causing transverse sliding and swivelling movement of the aft pair of capping beam feet relative to the skid base to thereby place the fore pair of skid-off feet in overlapping adjacent relationship to the aft ends of the cantilever beams, despite any limited misalignment.

9. An offshore drilling system comprising:

a floatable jack-up rig having downwardly extendable legs engageable with the sea bed to raise the rig'"'"'s hull from the sea surface, said rig having a pair of cantilever beams extending fore and aft in a longitudinal direction;

a fixed platform supported above the sea bed suspended by legs engaged with the sea bed having a pair of capping beams extending fore and aft in a longitudinal direction;

said jack-up rig in its floatable condition being maneuvered to a position in which the aft ends of said cantilever beams are positioned adjacent to the fore ends of said capping beams and the hull of said jack-up rig thereafter being raised by engaging said downwardly extendable legs with the sea bed and elevating the rig'"'"'s hull on said legs, to align a longitudinal axis of said jack-up rig with a longitudinal axis of said fixed platform;

said cantilever beams being extended in the same horizontal plane as said capping beams toward and closely spaced from the fore ends of said capping beams at less than a predetermined amount of misalignment between the longitudinal axes of said capping and said cantilever beams;

a generally rectangular skid base resting on said cantilever beams for longitudinal movement therealong to be transferred to said capping beams;

two longitudinally spaced fore and aft pairs of skid-off feet mounted to the underside of said skid base with one skid-off foot of each pair resting on an associated one of said cantilever beams, said skid-off feet supporting said skid base for longitudinal movement along said cantilever beams;

two longitudinally spaced fore and aft pairs of capping beam feet mounted to the underside of said skid base, the aft pair of capping beam feet being spaced aft of the aft pair of said skid-off feet and the fore pair of capping beam feet being spaced longitudinally between the fore and aft pairs of skid-off feet, each said capping beam foot being mounted to said skid base for movement in a direction transversely of said skid base and for swivelling movement about a vertical axis relative to said skid base;

said capping beam feet engaging said capping beams for longitudinal movement therealong while enabling simultaneous transverse and swivelling motion relative to said skid base during transfer of said skid base from said cantilever beams to said capping beams; and

,

whereby transfer of said skid base from said jack-up rig to said fixed platform can occur with reduced imposition of side loads on said capping beams, despite any misalignment less than the predetermined amount.

10. An offshore drilling system according to claim 9, further including:

a drill floor package initially mounted on said cantilever beams of said jack-up rig, forward of said skid base, for movement along said cantilever beams,

a pair of spur beams projecting forwardly from the forward end of said skid base adjacent to its upper surface, said spur beams having a downward-facing locking slot adjacent their forward ends;

said cantilever beams having a locking pin secured to their forward ends moveable vertically into and out of said locking slot in an associated one of said spur beams;

said rig, subsequent to transfer of said skid base to said capping beams, being raised vertically on its legs to cause said locking pin to enter said locking slots to cause said cantilever beams to become locked to said skid base against relative longitudinal separation with the upper surfaces of said skid base, said spur beams and said cantilever beams lying in substantially the same horizontal plane; and

,

whereby said drill floor package may be moved aft along said cantilever beams and across said spur beams onto said skid base.

11. An offshore platform used in drilling oil and gas wells, comprising:

a drill floor package having a derrick and a drill floor substructure supporting said derrick;

a platform supported above the surface of the water by legs engaging the sea bed, said platform having two beams that horizontally run from a fore portion of said platform to an aft portion; and

,

a skid base supporting said drill floor package, said skid base having a plurality of separate feet that vertically extend downward from an underside of said skid base into engagement with said beams, each foot including a movement mechanism that selectively provides axial movement of each said foot in relation to said beams when engaged, said movement mechanism including a walking mechanism having at least two legs that alternately support said skid base, and that also move between two relative spaced positions, whereby said skid base may move upon said beams and support said skid base substantially out of contact with said beams during axial movement, such that said skid base may be moved along said beams without substantial sliding friction between said beams and said skid base.

12. An offshore platform according to claim 11, wherein:

said skid base mounts upper rails, said upper rails running from side-to-side; and

,

said drill floor package being supported thereon for transverse motion of said derrick relative to said skid base.

13. An offshore platform used in drilling oil and gas wells, said offshore platform being attended by a jack-up rig positioned closely nearby, the jack-up rig having two parallel cantilever beams each having a locking pin, said offshore platform comprising:

a drill floor package having a derrick and a drill floor substructure supporting said derrick;

a fixed platform supported above the surface of the water by legs engaging the sea bed, said fixed platform having two capping beams that horizontally run from a fore portion of said fixed platform to an aft portion; and

,

a skid base supporting said drill floor package, said skid base having

a plurality of separate capping beam feet that vertically extend downward from an underside of said skid base into engagement with said capping beams, each capping beam foot including a movement mechanism that selectively provides axial movement of said skid base in relation to said capping beams when engaged, thereby enabling said skid base to move in relation to said capping beams upon said feet,

an upper surface of said skid base, said drill floor package being supported thereon for transverse motion of said derrick relative to said skid base, and

two spur beams that each mount a locking slot, said locking slot adapted to engage a locking pin of a corresponding cantilever beam, said locking slot mounted in relation to said locking pin such that an upper side of said spur beams align, when said locking pin is engaged with said locking slot, in flush rigid alignment with the upper surfaces of the cantilever beams of the jack-up rig;

wherein the upper surfaces of said spur beams are thereby adapted to support the transfer said drill floor package between the cantilever beams of the jack-up rig and said upper surface of said skid base.

14. An offshore platform for drilling oil and gas wells, said offshore platform being attended by a jack-up rig having two parallel cantilever beams that are extended in generally adjacent parallel orientation to said capping beams, comprising:

a drill floor package having a derrick and a drill floor substructure supporting said derrick;

a fixed platform supported above the surface of the water by legs engaging the sea bed, said fixed platform having two capping beams that horizontally run from a fore portion of said fixed platform to an aft portion; and

,

a skid base supporting said drill floor package, said skid base having two distinct sets of feet including

a plurality of separate capping beam feet that vertically extend downward from an underside of said skid base into engagement with said capping beams, each capping beam foot including a movement mechanism that selectively provides axial movement of said skid base in relation to said capping beams when engaged, thereby enabling said skid base to move in relation to said capping beams upon said feet, and

a plurality of skid-off feet that are also vertically disposed beneath said skid base and are adapted to be engaged with the cantilever beams and to support said skid base thereon; and

,

wherein at least two of said skid-off feet also each include a movement mechanism that provides movement to said skid base upon said skid-off feet between said fore and aft portions of the jack-up rig.

15. An offshore platform according to claim 14, wherein:

said skid base includes at least one skid base beam that extends from side-to-side on the underside of said skid base, said skid base beams adapted to extend across a space between said cantilever beams and to support said skid base with respect to said cantilever beams, at least one of said skid base beams mounting a pair of said capping beam feet;

said capping beam feet each include

a swivel mechanism that enables said movement mechanism of each capping beam foot to be swivelled with respect to said skid base beams, such that the axial movement of said movement mechanisms may be oriented to use said capping beams as rails, notwithstanding limited misalignment between the two, and,

a sliding mounting that mounts each said capping beam foot to said skid base beams for movement transversely to said skid base, such that said movement mechanism may be moved transversely with respect to said skid base beams, and such that axial movement of said movement mechanisms may be aligned to use said capping beams as rails, notwithstanding limited misalignment between the two.

16. An offshore platform according to claim 15, wherein:

said skid base includes at least one of said skid base beams mounting each said skid-off foot;

said skid-off feet include at least two fore skid-off feet that are the first skid-off feet to support said skid base upon the cantilever beams when said skid base is loaded from said offshore platform to the jack-up rig, each of said fore skid-off feet including

a sliding mounting that mounts said fore skid-off feet to mounting ones of said skid base beams, such that said fore skid-off feet may be transversely aligned to use the cantilever beams as rails, notwithstanding any misalignment between the two.

17. An offshore platform according to claim 14, wherein:

said capping beam feet include at least two aft capping beam feet that are the first capping beam feet to be moved upon said capping beams when said skid base is loaded to said offshore platform from the jack-up rig;

said skid-off feet include at least two aft skid-off feet that are the first skid-off feet to be removed from said skid base upon the cantilever beams when said skid base is loaded to said offshore platform from the jack-up rig; and

said offshore platform further comprises an aft vertical jack mechanism, moveable between retracted and extended positions, for causing weight of said skid base to be transferred to the cantilever beams from said capping beams (as said aft skid-off feet are engaged with the cantilever beams and said capping beam feet are disengaged with said capping beams, by relative lengthening of said aft skid-off feet in relation to said aft capping beam feet by said vertical jack means) and from the cantilever beams to said capping beams (as said aft skid-off feet are shortened relative to said capping beam feet by said vertical jack means, thereby disengaging said aft skid-off feet with the cantilever beams and causing said aft capping beam feet to engage said capping beams and support said skid base thereon).

18. An offshore platform for drilling oil and gas wells comprising:

a drill floor package having a derrick and a drill floor substructure supporting said derrick;

a fixed platform supported above the surface of the water by legs engaging the sea bed, said fixed platform having two capping beams that horizontally run from a fore portion of said fixed platform to an aft portion;

a skid base supporting said drill floor package, said skid base having a plurality of separate capping beam feet that vertically extend downward from an underside of said skid base into engagement with said capping beams, each capping beam foot including a movement mechanism that selectively provides axial movement of said skid base in relation to said capping beams when engaged, thereby enabling said skid base to move longitudinally upon said capping beam feet;

a source of fluids and semi-solids for supporting drilling operations of said drill floor package; and

piping for connecting said drill floor package with said source across a distance dimension that changes as said skid base is moved upon said capping beams, said piping including a plurality of discrete pipe modules, each module having a plurality of conduits of predetermined arrangement, all of said conduits in a given module having substantially the same length, such that modules may be coupled in modular format to form said piping and may be individually added or subtracted as said skid base is moved longitudinally upon said capping beams.

19. A skid base adapted to support a drill floor package, and further adapted be transferred between capping beams of an offshore platform and cantilever beams of a jack-up rig, said skid base comprising:

a skid structure having an upper surface adapted to support the drill floor package, and an underside of sufficient width to be supported upon both of the capping beams and the cantilever beams;

a plurality of foot assemblies mounted by and disposed vertically below said underside of said skid structure, each of said plurality of foot assemblies adapted to be engaged with support beams that are one of the capping beams and the cantilever beams and adapted to bear weight of, and to support, said skid base upon said support beams;

wherein each foot assembly is mounted to said skid base by an adjustable mounting that permits said plurality of foot assemblies to be varied in their relative spacings from one another along a width dimension of said underside, such that said plurality of foot assemblies may be aligned in their relative spacings to match a spacing associated with the said supporting beams.

20. A skid base according to claim 19, wherein at least one foot assembly includes a movement mechanism that is adapted to provide relative axial movement between said skid base and said supporting beam.

21. A skid base according to claim 20, wherein:

said movement mechanism provides relative axial movement; and

,

each of said foot assemblies having said movement mechanism also includes a swivel mechanism that enables said walking mechanism to be swivelled and aligned with said support beam for movement therealong.

22. A skid base according to claim 19, wherein said skid base further comprises at least one transverse base extension mounted to a flank of said skid structure for increasing the width of said underside and increasing a range of relative transverse movement of said foot assembly relative to said underside.

23. A foot assembly that supports a drill floor package upon the upper surface of an offshore platform, wherein the drill floor package is supported by parallel mounting beams and wherein the upper surface of the offshore platform has parallel capping beams that bear the load of the drill floor package, the parallel mounting beams being generally perpendicular in orientation to the parallel capping beams, the foot assembly comprising:

a first movement mechanism including a first bearing surface that allows relative motion of said foot assembly upon one of the parallel capping beams along a first linear direction;

a second movement mechanism including a second bearing surface that mounts said first movement mechanism to at least one of the parallel mounting beams and that allows relative motion between said foot assembly and the parallel mounting beams, the drill floor package supported thereby, along a second linear direction of the parallel mounting beams; and

,

a swivel mechanism positioned between said first movement mechanism and said second movement mechanism, for permitting relative swivelling movement therebetween.

24. A jack-up rig used to assist the drilling of oil and gas wells aboard a fixed platform, the fixed platform supported above the bed of the sea and having two parallel capping beams that run horizontally from a fore portion of the fixed platform to an aft portion, said jack-up rig comprising:

a jack-up body supporting two parallel cantilever beams each having a locking pin, said jack-up body also having legs extendable to elevate at said cantilever beams to a level above the sea bed at which it is substantially elevated to a level of the fixed platform above the sea bed;

a drill floor package having a derrick and a drill floor substructure supporting said derrick;

a skid base supporting said drill floor package, said skid base having

a plurality of separate capping beam feet that vertically extend downward from an underside of said skid base for engagement with said capping beams, each capping beam foot including a movement mechanism that selectively provides axial movement of said skid base in relation to said capping beams when engaged, thereby enabling said skid base to move in relation to said capping beams upon said feet,

an upper surface of said skid base, said drill floor package being supported thereon for transverse motion of said derrick relative to said skid base, and

two spur beams that each mount a locking slot that is adapted to engage said locking pin of a corresponding cantilever beam, said locking slot mounted in relation to said locking pin such that an upper side of said spur beams align, when said locking pin is engaged with said locking slot, in flush rigid alignment with the upper surfaces of the cantilever beams of the jack-up rig;

wherein the upper surfaces of said spur beams are thereby support the transfer said drill floor package between the cantilever beams of the jack-up rig and said upper surface when said skid base is transferred to and supported by the capping beams of the fixed platform.